1. Field of the Invention
The present invention relates generally to a taking lens drive unit, and more particularly to a taking lens drive unit which drives a zoom lens for use in an ENG camera, etc.
2. Description of Related Art
In the ENG camera, a lens drive unit is attached to the side of a lens barrel. A focus drive motor, a zoom drive motor, an iris drive motor, etc. are arranged in the drive unit. The rotational driving force of each motor is transmitted to a focus ring, a zoom ring and an iris ring in the lens barrel through a gear transmission mechanism.
When a cameraman takes a picture with the ENG camera on the shoulder, he or she inserts four fingers (other than the thumb) of the right hand into a grip band attached to the side of the drive unit to hold the lens barrel, and grips the focus ring at the end of the lens with the left hand to manually adjust a focus. The cameraman also manipulates a zoom seesaw control switch (hereinafter referred to as a seesaw switch) with the forefinger and the middle finger (or the ring finger) of the right hand, and manipulates a VTR switch with the thumb of the right hand.
In another conventional drive unit, a switch means (a control button) is provided in proximity to the VTR switch. Pressing the control button with the thumb of the right hand causes a zoom lens to be zoomed toward a telephoto end (or a wide end), and releasing the control button returns the zoom lens to the original position (the zoom position before the button is pressed). This function will hereinafter be referred to as a quick zooming.
The control button for the quick zooming (hereinafter referred to as a quick zoom switch) and the seesaw switch are constructed so that the switch pressed later can take priority during the zooming. If the quick zoom switch is pressed by mistake during the zooming with the use of the seesaw switch, the quick zooming is started. Particularly because the quick zoom switch is arranged close to the VTR switch, the quick zoom switch is frequently pressed by mistake with an intention of pressing the VTR switch.
The conventional drive unit is constructed in such a way that the maximum zoom rate is set by means of a maximum zoom rate control, etc., and the rate of the quick zooming is associated with the maximum zoom rate. The quick zooming is performed at the rate which is set by means of the maximum zoom rate control. Accordingly, if the maximum zoom rate is low, the quick zooming is performed slowly, and it is impossible to perform the quick zooming quickly.